Optical near-field lithography on hydrogen-passivated silicon surfaces

Abstract

We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced by the optical near field, were observed after etching in potassium hydroxide. The uncoated fibers can also induce oxidation without light exposure, in a manner similar to an atomic force microscope, and linewidths of 50 nm have been achieved this way.

Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

“…Since the sample is illuminated through an uncoated fiber probe, we have previously proposed that the narrow central peak is due to the optical near-field emitted from the very end of the SNOM probe, whereas the broader side peaks are due to an optical interference pattern mainly dominated by the far-field penetrating the sidewalls of the uncoated probe. 10 The full width at halfmaximum of the central peak is ϳ115 nm. The typical linewidth of the side peaks is 215-225 nm, and the average peak-to-peak distance between the central peak and the side peaks is 245 nm.…”

“…De-convoluting the shape of the AFM tip, the actual linewidth may be as narrow as 35 m. Also, we do not observe any oxidation when the light to the probe is switched off, in contrast to unexpected oxidation effects that have been reported previously with uncoated fiber probes under no illumination. 10 …”

“…4,8 More recently, optically induced hydrogen desorption was reported. [9][10][11] In this article we discuss results obtained using a scanning near-field optical microscope ͑SNOM͒ 12 to generate an oxide mask on an amorphous silicon ͑a-Si͒ layer. Results for uncoated fiber probes are compared with those for aluminum-coated probes.…”

“…Line scans with an uncoated fiber display a three-peak profile after etching the surface in potassium hydroxide ͑KOH͒. 10 Numerical simulations based on a macroscopic self-consistent model 13,14 have been used to explain the experimental observations. Taking the uncertainty of the precise shape of the probe into account, the model was found to be in good agreement with the observed silicon structures.…”

Nanofabrication with proximal probes

“…Kramer et al [26] used HF-passivated and STM-oxidized a-Si H as a resist layer to etch fine metal wires. In a similar approach, Minne et al [27] were successful in patterning a variety of structures (including a 0.1-m gate MOSFET) by using reactive ion etching to selectively etch an AFM-patterned a-Si H resist layer, and Madsen et al have used both optically induced depassivation and the AFM to oxidize and pattern such layers [28]. These accomplishments are significant because they demonstrate a general application of the anodic oxidation and selective etching process to a variety of material systems by using easily deposited a-Si H films as a resist layer.…”